"Er isst keine rote Suppe."
Kein is used in both situations: either instead of "not a/an" (it means the negative + article) or instead of "not" in case there is no article. To differ between those two situations you have to know the context and the following noun and then it is the same like in normal spoken English. You're not putting the article when it is not common.
How come that in this case, it is "Er isst keine rote Suppe" - the "keine " is what concerns me. In previous sentence about dark beer, the solution was "Wir haben kein schwarzes Bier" - why not "keines" then? I mean, in the 1st sentence the 'keine' takes on the fem accus ending per following noun die Suppe. In the 2nd sentence, the 'kein' does not take on the appropriate neuter accus ending of the following noun das Bier. I am sure I've missed something somewhere, but for the life of me....where ?!? Please help.
Suppe is feminine :)
Edit: Also mixed inflection http://en.wikipedia.org/wiki/German_declension#Mixed_inflection.5B6.5D
I did find the table and the"euer klares Wasser" (mixed/accus/neuter) which I believe is the appropriate example for "kein schwarzes Bier"
I do understand the "rote Suppe" sentence above because it follows my logic. However, the preceding practice sentence does not follow the same logic. I should have posted my comment in the previous exercise, but I am a slow thinker anymore. My bad.
Now my problem.
Point 1. How do you say "We do not have any beer." ??? Isn't it: "Wir haben keines Bier" ??? - at least that's what I think is correct. If I am wrong, my whole problem is pointless, and I must review my accusative weaknesses :)
If I am right, however, my question is:
Why not "Wir haben keines schwarzes Bier" ??? Why is it "Wir haben kein schwarzes Bier." ??? Is it just convention and thus a rule because an indefinite article precedes an accusative adjective which precedes a neuter noun ????
Sorry for being annoying.